Refrigerated case with anti-condensation control system

ABSTRACT

A refrigerated case for storing food product includes a sensor module and a control module. The control module receives input from the sensor module and compares the input to a set point to generate an output indicative of a difference between the input and the set point, and further updates the output based on the input from the sensor module. A heater module controls a heater attached to a control surface of the refrigerated case based on the output to maintain a temperature of air adjacent the sensor module above a dew point temperature of room air.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/124,909 filed on May 9, 2005, which claims the benefit of U.S.Provisional Application No. 60/569,581 filed on May 10, 2004. Thedisclosures of the above applications are incorporated herein byreference.

FIELD

A system and method for preventing condensation and, more particularly,a system and method for operating anti-condensation heaters.

BACKGROUND

Refrigerated spaces such as refrigerated display cases, walk-inrefrigerators, and walk-in freezers commonly include heaters to preventcondensation from forming on certain areas of the device from watervapor present as humidity in the surrounding air. For example, walk-inrefrigerators and freezers typically employ a heater to preventcondensation from forming on air vents, personnel doors, drain lines,and observation windows. Similarly, refrigerated display cases such ascoffin cases, island cases, and tub cases typically employ a heater toprevent condensation from forming on and around an opening and/or doorof the display case.

For example, glass-door refrigerated display cases are frequently usedin supermarkets and convenience stores and often include heaters in theglass doors and the door frames to prevent condensation on the glassfrom humid air. The glass doors and frames are typically heated to atemperature above the dew-point temperature of the air in the room inwhich the display cases are located to prevent condensation.

Prior art control systems apply heat to the glass doors in proportion toa measured dew point in an open-loop system. Manual intervention, in theform of manually adjusting the control scheme, is required to achievecondensation-free doors. The adjustment process is prone to human error,typically resulting in setting the heat too high and losing some of thepromised energy savings. Also, such adjustments usually are made at aparticular operating condition, and may not work correctly year roundwhere climate changes are more drastic, as dew point and conditionschange with the season. Further, the adjustment process is timeconsuming and does not result in a known door temperature.

One method of controlling the amount of heat applied to the display casedoors includes applying full power (i.e., line voltage, typically) tothe door heaters. The applied heat prevents condensation but wastesenergy as more heat is applied than is necessary. The excess energyconsumed by the door heaters directly increases the cost of operatingthe refrigeration system. Such costs are further increased as excessenergy in the form of heat is dissipated into the refrigerated space andmust be removed by the refrigeration system.

Other control systems modulate the heat applied to the display casedoors and, as a result, reduce door heat energy and related costs. Suchsystems generally control the applied proportion of maximum heat, whichis proportional to the square of line voltage to adjust the heat appliedto the doors. While such systems adequately reduce the amount of heatapplied to the doors, such systems suffer from the disadvantage of beingsusceptible to variations in line voltage and are therefore not precise.

For example, as illustrated in FIG. 1, a prior art proportionalcontroller has one or more adjustments to allow a user to adjust a doorheater between a minimum and a maximum in response to variation of dewpoint of the room air (i.e., more heat for higher dew point). Somesystems permit limiting the upper and lower limits of the heatmodulation to values other than zero and one hundred percent, e.g.,limiting the heat to a twenty percent minimum and a ninety percentmaximum. Others have a simple rotary dial that adjusts a gain or anoffset. Still others define limits as endpoints of a line, asillustrated in FIG. 2, which shows control over a 3-segment line.Segment 1, which is at a low dew point, shows modulation held at twentypercent of full heat. In segment 2, modulation varies with dew pointsbetween 25 and fifty degrees F. dew point. In segment 3, modulation isninety percent, of full heat, for high dew points.

SUMMARY

A refrigerated case for storing food product including a sensor moduleand a control module receiving input from the sensor module andcomparing the input to a set point to generate an output indicative of adifference between the input and the set point. The control moduleupdates the output based on the input from the sensor module. A heatermodule controls a heater attached to a control surface of therefrigerated case based on the output to maintain a temperature of airadjacent the sensor module above a dew point temperature of room air.

A bank of refrigerated cases for storing food product includes a sensormodule having a first sensor positioned adjacent a control surface of atleast one of the refrigerated cases and a control module that receivesan input from the sensor module and compares the input to a set point togenerate an output indicative of a difference between the input and theset point. The control module updates the output based on the input fromthe sensor module. A heater module controls a heater attached to thecontrol surface of the at least one of the refrigerated cases based onthe output to maintain a temperature of air adjacent the first sensorabove a dew point temperature of room air.

Further areas of applicability of the present teachings will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples areintended for purposes of illustration only and are not intended to limitthe scope of the teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a schematic representation of a prior art proportionalcontroller;

FIG. 2 is a graph showing percentage heat modulation versus temperaturefor a prior art door heater control system;

FIG. 3 is a schematic representation of an anti-condensation controlscheme in accordance with the present teachings;

FIG. 4 is a cross-sectional view of a relative humidity sensorincorporating a drip-shielding baffle and disposed within a door casingor door frame;

FIG. 5 is a cross-sectional view of a relative humidity sensor showingthe drip-shielding baffle of FIG. 4 from another direction;

FIG. 6 is a perspective view of an air flow path of a relative humiditysensor incorporating a housing having an open bottom portion and an airpassage formed in a side wall;

FIG. 7 is a perspective view of a relative humidity sensor in accordancewith the principles of the present teachings incorporating a housinghaving a pair of air passages formed in a side wall;

FIG. 8 is a perspective view of a relative humidity sensor in accordancewith the principles of the present teachings incorporating a housinghaving a pair of air passages formed in another side wall;

FIG. 9 is a psychrometric chart for use with the anti-condensationcontrol scheme of FIG. 3;

FIG. 10 is another psychrometric chart for use with theanti-condensation control scheme of FIG. 3, wherein water vapor is attwice the amount as the psychrometric chart of FIG. 9;

FIG. 11 is a schematic representation of another anti-condensationcontrol system in accordance with the principles of the presentteachings; and

FIG. 12 is a schematic representation of the control system of FIG. 11applied to a plurality of doors.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the teachings, its application, or uses.

The control system and method achieves a temperature slightly higherthan the dew point of humid air adjacent a control surface of acomponent of a refrigeration device to prevent condensation from formingon the control surface. For example, the control system maintains airadjacent a door of a refrigerated display case, or an observation windowof a walk-in refrigerator or freezer, slightly above the dew point ofhumid air adjacent the door or observation window to maintain therespective component free from condensation. Thus, the relative humidityof the humid air adjacent the component (the air which has been cooledto component temperature) is high, but less than one hundred percent.Because humid air has a dew point, or temperature at which relativehumidity is one hundred percent, cooling the humid air to a temperaturebelow the dew point causes water vapor to condense.

If the temperature of the component (i.e., glass door or observationwindow) is below the dew point of the humid air in the room where thecomponent is located, the cool air of the room will cool the humid airat the component below the dew point, which will cause moisture tocondense thereon. But, if the temperature of the component is slightlyabove the dew point of room air, the humid air touching the componentwill be cooled, but not to the point of causing condensation.

The system and method according to the present teachings may be used ina variety of refrigeration and freezer applications such as, but notlimited to, display cases, walk-in refrigerators, and walk-in freezers,to control the temperature of any control surface. For example, walk-inrefrigerators and freezers could employ the present system to preventcondensation from forming on air vents, personnel doors, drain lines,walls, and observation windows. Similarly, refrigerated display casessuch as coffin cases, island cases, and tub cases could employ thepresent system to prevent condensation from forming on any wall orsurface surrounding an opening and/or door of the display case. Whilethe present system is applicable to each of the aforementionedrefrigeration and freezer applications, the present system will bedescribed in association with a refrigerated display case having a glassdoor.

To achieve the system and method according to the present teachings, arelative humidity sensor 10 may be mounted on a control surface, such asa door 12 or other structure of a refrigerator/refrigerated case 14,such that the sensor itself, and the air it monitors, are cooled to acontrol surface temperature. The sensor 10 may be mounted to any portionof the door 12 or structure of the refrigerator/refrigerated case 14 solong as the structure to which the sensor 10 is mounted is indicative ofthe temperature of the control surface.

For example, if a glass pane of the door 12 is deemed the controlsurface (i.e., the portion of the door 12 to maintain free fromcondensation), the sensor 10 may be mounted directly to the glass paneor, alternatively, to support structure either on the door 12, such as adoor casing 25 generally surrounding the glass pane, or to surroundingsupport structure, such as a door frame 26 that operably supports thedoor 12. The door casing 25 and door frame 26 are schematicallyrepresented in FIGS. 4 and 5. The sensor 10 may be mounted either on theglass pane, door casing 25, or door frame 26 or within the glass pane,door casing 25, or door frame 26, provided that the respective structureis generally at the same temperature as the control surface. By mountingthe sensor 10 in close proximity to the control surface, the sensor 10is able to accurately measure the relative humidity of air adjacent thecontrol surface.

Mounting the RH sensor 10 within the door casing 25 or door frame 26protects the sensor 10 from dust, moisture, or other liquids. Forexample, the sensor 10 and appropriate drip protection or baffles 30,may be arranged on a small plate, which is mounted in a hole cut intothe door casing 25 or door frame 26. The casing 25 or frame 26 may befurther modified to include air vents 32, such as screens, louvers orsmall holes, generally above and below the sensor location. By locatingthe sensor 10 approximately in the middle portion of a vertical portionof the door casing 25 or door frame 26, adequate air flow over thesensor 10 may provide a reliable relative humidity measurement. Sucharrangements are shown in FIGS. 4 and 5.

The RH sensor 10 may be arranged in a thin vertical tube 27 (representedschematically in FIGS. 4 and 5) having baffles 30 near the sensor 10 toprevent moisture or dust from falling on the sensor 10, and to preventwater or other cleaning solutions from dripping onto the sensor 10. Thevertical tube 27 may be thermally in contact with the door 12, so thatthe tube 27 is at approximately the same temperature as the door 12. Thetube 27 may permit air flow vertically, so that air passes by therelative humidity sensor 10 located inside the tube 27. The tube 27should be long enough to cool air passing therethrough to doortemperature, or close to door temperature, before passing over thesensor 10. Furthermore, the tube 27 should have a path long enough forcooling air both above and below the sensor 10 so that the air is cooledbefore reaching the sensor 10, regardless of the direction of air flow(i.e., due to air currents in the room can cause flow in eitherdirection).

While the RH sensor 10 may be mounted within a door casing 25, doorframe 26, and/or tube 27 including air inlets and outlets 32 at the topand bottom thereof to accommodate air flow, air inlets 32 may also, oralternatively be, located on the front or the sides of the respectiveassembly (i.e., casing 25, frame 26, or tube 27), which lessens theopportunity for water to drip into the assembly or dust to collect onthe assembly. Such an arrangement may be useful where the RH sensor 10is not mounted inside the door frame 26 (e.g., when mounted on anexternal surface of the door frame 26). Possible arrangements are shownin FIGS. 6, 7, and 8.

FIGS. 6 and 7 illustrate air entry and exit holes 32 on a front surface36 of the door casing 25, door frame 26, and tube 27 with thearrangement of FIG. 7 having an open bottom for air flow. FIG. 8illustrates air entry and exit holes 23 on sides 38 of the door casing25, door frame 26, and tube 27. Note, however, that the air entry andexit holes may be on both sides or, if mounted on the door frame 26,preferably on the side toward the door glass only. The RH sensor 10 maybe made as thin as practical, measuring from front to back, to sense airas close to the door surface as possible, and thus nearly at doortemperature. Furthermore, casing 25, frame 26 and tube 27 may be open orclosed at both ends to tailor the flow of air therein. Such arrangementsmay be particularly appropriate for RH sensors 10 not mounted inside adoor frame 26.

While the RH sensor 10 is described as being associated with a door of arefrigerator/refrigerated case, it should be understood that the sensor10 may alternatively be used with an open refrigerator/refrigerated caseor a walk-in refrigerator/freezer. In such applications, the sensor 10can be mounted on any surface to be controlled (i.e., for whichprevention of condensation is desired), such as walls, windows, doors,housing rails, or other support structure.

An anti-condensation control system 13 employing a heater controller 15having an adder-subtractor 16, a proportional integral controller (PID)18, a limiter 20, and a heater modulator 22 is illustrated in FIG. 3.The RH sensor 10 provides an input to the adder-subtractor 16, whichalso receives a RH set point as an input. The set point may be providedat ninety percent, and the adder-subtractor 16 determines an error,which is input to the PID controller 18 to determine an output betweenzero and one hundred percent. The output may be applied to the limiter20 having a percent minimum and percent maximum output to be applied tothe heater modulator 22, which controls a door heater 24 as the RHsensor 10 at the door 12 continues to supply an input to theadder-subtractor 16 for comparison to the set point. Thus, theanti-condensation control system 13 provides closed-loop control. Whilea PID controller is disclosed, other control logic, such as, but notlimited to, fuzzy logic, may also be used with the control system 13,and should be considered within the scope of the present teachings.

The control system 13 according to the present teachings may have a setpoint at a relatively high RH value, such as ninety or 95 percent. TheRH set point may be adjusted for lack of accuracy in the RH sensor 10 orto account for temperature variations at different areas of the door 12.For example, if parts of the door 12 are cooler than the air flowingover the RH sensor 10, a lower RH set point (RHSP) may be appropriate,such as lowering the RHSP to eighty percent. Lowering the RHSP ensuresthat the entire door 12 remains free from condensation by applyingadditional heat to cooler areas of the door 12.

The set point may never have to be adjusted, particularly if there is acontrol system for each door 12. In such systems, it is not necessary toprovide accessibility to the system to make adjustments to the set pointas user intervention is not required to properly adjust the controlsystem 13. This feature, in system design, may result in considerablecost savings.

With reference to FIG. 9, operation of the control system 13 can beillustrated by plotting an example on a psychrometric chart. The systemcontrol goal is to maintain relative humidity at the RH sensor 10 atninety percent relative humidity, i.e., RHSP equaling approximatelyninety percent. In a room having a dry bulb temperature of +68 degreesF. and relative humidity of 36.9 percent (away from the refrigeratedsurfaces), the dew point is +40 degrees F., which is determined byextending a line horizontally from the air condition to a point on theone hundred percent RH curve in FIG. 9. The control point is where thatsame horizontal line intersects ninety percent RH, and the heatermodulator 22 will apply just enough heat to bring the door temperatureto +42.7 degrees F., which is slightly above the dew point. Further, ifthe RH sensor 10 indicates 95 percent relative humidity, the controller15 would apply more heat as the door temperature is +41.3 degrees F. Ifthe RH sensor 10 indicates 85 percent relative humidity, the controller15 would reduce the heat being applied, as the door temperature is +44.2degrees F. Thus, the controller 15 will adjust the heat applied untilthe RH sensor 10 achieves ninety percent relative humidity.

Another psychrometric chart is illustrated in FIG. 10, where water vapor(i.e., airborne moisture, humidity) is present at approximately twicethe amount as in the example of FIG. 9, which is noted on the verticalaxis of the psychrometric chart of FIG. 10. Where FIG. 9 included 0.0052pounds of moisture per pound of dry air, FIG. 7 illustrates 0.0107pounds of moisture per pound of dry air. While in FIG. 9, DT minus DPequals 2.7 degrees F., the differential in FIG. 10 is 3.0 degrees F. Inboth situations, however, controlling the heat to maintain the RH sensor10 at ninety percent relative humidity causes the door temperature to beabout 3 degrees F. above the dew point. This approximate differential ofdoor temperature over dew point is true over a wide variation ofairborne moisture or humidity.

A separate control system 13 may be applied to each door 12 of arefrigerated display case such that one controller 15 may be used tocontrol heaters 24 for a plurality of doors 12. For example, the RHsensor 10 may be located in the side of one door 12 that is closest toanother door 12 sought to be controlled, (i.e., adjacent doors 12) tocontrol both doors 12. The heaters 24 of both doors 12 may be connectedin parallel and be driven by the same controller 15. For three adjacentdoors 12, the RH sensor 10 may be mounted in the middle door 12. Theheaters 24 of all three doors 12 may be connected in parallel and bedriven by one controller 15. The system and method may include threedifferent heater outputs, all modulated in the same way, but each outputpowered by a different phase of three-phase power.

In a system incorporating multiple doors 12, each anti-condensationsystem 13 may be monitored and tracked separately to diagnose faultsassociated with each door 12 and/or system 13. In this manner, eachsystem 13 may be in communication with a main controller 34 that trackssystem performance and updates the RH set point, when necessary. Therefrigeration controller 34 is preferably an Einstein of E2 AreaController offered by CPC, Inc. of Atlanta, Ga., or any other type ofprogrammable controller that may be programmed.

Another apparatus and method for preventing condensation includescontrolling component temperature in relation to a measured dew point inorder to minimize heater energy use. A closed-loop control system 40according to the present teachings efficiently prevents condensation andlowers energy use, while providing automated adjustment of the system40. Like control system 13, control system 40 may be used in a varietyof refrigeration and freezer application such as, but not limited to,display cases, walk-in refrigerators, and walk-in freezers. For example,the control system 40 may be employed in walk-in refrigerators andfreezers to prevent condensation from forming on air vents, personneldoors, drain lines, and observation windows. Similarly, refrigerateddisplay cases such as coffin cases, island cases, and tub cases couldemploy the control system 40 to prevent condensation from forming on andaround an opening and/or door of the display case. While the controlsystem 40 is applicable to each of the aforementioned refrigeration andfreezer applications, the control system 40 will be referred tohereinafter and in the drawings as associated with a refrigerateddisplay case having a glass door.

As shown in FIG. 11, the apparatus and method includes measuring andcontrolling door temperature to a temperature equal to dew-pointtemperature of the room air, plus a delta temperature offset. Thus, thedoor temperature is held at slightly above dew-point temperature, whichis an optimum door temperature for preventing condensation with minimumheat applied to the doors 12.

With reference to FIG. 11, the anti-condensation control system 40 isshown including a dew-point sensor 42 and a heater controller 41 havinga math block 43, an adder-subtractor 44, a proportional integralcontroller (PID) 48, a limiter 50, and a heater modulator 52. Thedew-point sensor 42 provides a temperature measurement to theadder/subtractor 44, which also receives a delta temperature offset foradjusting the measurement received by the dew-point sensor 42. Further,the adder/subtractor 44 receives a temperature measurement from atemperature sensor 46 located on the door 12 of the refrigerated displaycase and determines an error value between the dew-point sensor inputplus the delta temperature offset, and the temperature measurementreceived from the temperature sensor 46. This error value is applied tothe proportional integral derivative (PID) controller 48, which outputsa percentage to the limiter 50, which limits the output percentage to apredetermined percentage minimum and/or percentage maximum. The limiter50 outputs an adjusted demand signal to the heater modulator 52, whichthen applies heat to the doors 12 via heater 54 in accordance with therequired demand. While a PID controller is disclosed, other controllogic, such as, but not limited to, fuzzy logic, may also be used withthe control system 40, and should be considered within the scope of thepresent teachings.

In addition to the foregoing, the control system 40 may include arelative humidity sensor 55 and a temperature sensor 57 in place of thedew-point sensor 42, and a math block 43 in the heater controller 41.The relative humidity sensor 55 detects door temperature relativehumidity and supplies an input indicative thereof to the math block 43while the temperature sensor 57 measures ambient temperature andprovides an input indicative thereof to the math block 43. The mathblock 43 computes the dew point based on the inputs from the relativehumidity sensor 55 and temperature sensor 57. Therefore, the controlsystem 40 could employ a stand-alone dew-point sensor 42 or could use amath block 43 in conjunction with a relative humidity sensor 55 and atemperature sensor 57 to compute the dew point. In either event, the dewpoint is fed to the adder-subtractor 44 for processing, as previouslydiscussed.

In a system incorporating multiple doors 12, the performance of eachanti-condensation system 40 may be separately monitored and tracked todiagnose faults associated with each door 12 and/or system 40. In thismanner, each system 40 may be in communication with a system controller59 that tracks system performance and updates system parameters, whennecessary.

In FIG. 12, a dew-point sensor 42 for the room provides an input fortemperature control of multiple doors 12, which collectively are subjectto a single delta temperature offset. Doors with different heat loads,such as when one is open, are all precisely controlled to a temperaturejust above the dew point. It should be understood that the arrangementshown in FIG. 12 may alternatively include a relative humidity sensor 55and a temperature sensor 57 (with math blocks 43 in the heatercontrollers 41) in place of the dew-point sensor 42.

The system and method may also include a temperature sensor 46 on onedoor 12, but the system and method controls heaters 54 in all similardoors 12, for example, a group of doors 12 for a single refrigerateddisplay case or a circuit, based on a single door temperature sensormeasurement. While this arrangement provides lower installation cost byeliminating multiple door temperature sensors 46, it may require ahigher delta temperature offset to ensure that other door temperaturesremain above the dew point for dependable prevention of condensation onall the doors 12. Accordingly, the energy cost savings may be less thanan arrangement where each door 12 includes its own door temperaturesensor 46.

A similar arrangement would include a door temperature sensor 46 foreach door 12, but the door temperatures being averaged before beinginput to the PID controller 48. A similar variation would include a doortemperature sensor 46 for each door 12, but apply the minimum doortemperature to the PID controller 48. For this arrangement, each door 12would remain above the dew-point temperature, but may not result in themaximum energy savings because some door temperatures may be relativelyhigh compared to the dew-point temperature.

As described above for the RH sensors 10, the door temperature sensors46 can be arranged on the glass, on the frame 26, in the frame 26, orany of the variations discussed above, as well as any reasonablealternatives.

The description is merely exemplary in nature and, thus, variations areintended to be within the scope of the teachings and are not to beregarded as a departure from the spirit and scope of the teachings.

1. A refrigerated case for storing food product comprising: a sensormodule; a control module receiving an input from said sensor module andoperable to compare said input to a set point and generate an outputindicative of a difference between said input and said set point, saidcontrol module updating said output based on said input from said sensormodule; and a heater modulator operable to control a heater attached toa control surface of the refrigerated case based on said output tomaintain a temperature of air adjacent said sensor module above a dewpoint temperature of room air.
 2. The refrigerated case of claim 1,wherein said control module uses closed-loop control to control saidheater.
 3. The refrigerated case of claim 1, wherein said sensor moduleincludes a sensor mounted to a control surface selected from the groupcomprising a glass pane, a casing, a frame, a rail, or a wall of therefrigerated case.
 4. The refrigerated case of claim 1, wherein saidsensor module includes a temperature sensor.
 5. The refrigerated case ofclaim 1, wherein said sensor module includes a relative humidity sensor.6. The refrigerated case of claim 5, wherein said sensor module includesa temperature sensor, said control module determining a dew point basedon information received from said relative humidity sensor and saidtemperature sensor.
 7. The refrigerated case of claim 1, wherein saidsensor module includes a dew point sensor.
 8. The refrigerated case ofclaim 1, wherein said control module includes a controller and at leastone of an adder-subtractor and a limiter.
 9. The refrigerated case ofclaim 1, wherein said control module is in communication with a maincontroller.
 10. A bank of refrigerated cases for storing food productcomprising: a sensor module having a first sensor positioned adjacent acontrol surface of at least one of the refrigerated cases; a controlmodule receiving an input from said sensor module and operable tocompare said input to a set point and generate an output indicative of adifference between said input and said set point, said control moduleupdating said output based on said input from said sensor module; and aheater modulator operable to control a heater attached to said controlsurface of said at least one of the refrigerated cases based on saidoutput to maintain a temperature of air adjacent said first sensor abovea dew point temperature of room air.
 11. The bank of refrigerated casesof claim 10, wherein said control module uses closed-loop control tocontrol said heater.
 12. The bank of refrigerated cases of claim 10,further comprising a plurality of sensor modules respectively associatedwith each refrigerated case.
 13. The bank of refrigerated cases of claim10, wherein said first sensor is a temperature sensor.
 14. The bank ofrefrigerated cases of claim 10, wherein said sensor module furtherincludes a second sensor.
 15. The bank of refrigerated cases of claim14, wherein said second sensor is a relative humidity sensor.
 16. Thebank of refrigerated cases of claim 15, wherein said control moduledetermines a dew point based on information received from said relativehumidity sensor and said first sensor.
 17. The bank of refrigeratedcases of claim 16, wherein said first sensor is a temperature sensor.18. The bank of refrigerated cases of claim 10, wherein said controlsurface is selected from the group comprising a glass pane, a casing, aframe, a rail, or a wall of said at least one of the refrigerated cases.19. The bank of refrigerated cases of claim 10, wherein said controlmodule is in communication with a main controller.
 20. The bank ofrefrigerated cases of claim 10, wherein said first sensor is a dew pointsensor.